Photo: Jeffrey Beall · CC BY 4.0Few U.S. towns get less rain and snow than New Castle: 12 inches a year
The warmest part of a July day comes in at 90° on average. In January, nights here are colder than in 87% of U.S. towns. Decade by decade the climate has edged up, 1.7° above 1901–2000. Plan time outside for May, June and September, when highs sit at 72–84°.
A year in New Castle at a glance
Each month’s typical high and low, and what it brings.
What stands out about New Castle’s climate
Compared with towns across the U.S., with New Castle’s place in Colorado beside it.
What a year in New Castle feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 142 frost-free days a year
In half of years the last 32° night comes by May 13 and the first by October 3. Frost and day counts come from NOAA’s station at Glenwood Spgs #2, CO, 12 miles from the town’s center, at about the same height.
The 2023 USDA map puts New Castle’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −9°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 39 inches of snow a winter
Snow, measured at Glenwood Spgs #2, CO, falls mostly in January. Precipitation (rain plus melted snow) adds up to 12 inches a year; September is the wettest month and June the driest. Rain or snow falls on about 75 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in New Castle
94% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Glenwood Spgs #2, CO.
Living with New Castle’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
142 frost-free days in zone 6a. The last frost comes by May 13 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 3.
Months with highs of 62–84° and lows of 40° or more: May, June and September. 19 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in New Castle from natural hazards, river flooding is the largest share (41%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →New Castle and similar climates
TownRatings has no climate map of the towns around New Castle yet.
Climates most like New Castle’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| New Castle, CO | 14° | 90° | 12" | 39" |
| Elko, NV | 15° | 90° | 10" | 41" |
| Scottsbluff, NE | 15° | 90° | 15" | 43" |
| Torrington, WY | 14° | 90° | 13" | 31" |
| Hyde Park, UT | 14° | 89° | 16" | 44" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in New Castle averaged 1.7° warmer than the 1900s. The biggest change is in March (+3.2°).
A bigger shift than in 70% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How New Castle compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with New Castle’s place among Colorado’s.
New Castle weather by month
Highs, lows and precipitation from NOAA’s grid at New Castle’s center; snow, wet days and snow on the ground from Glenwood Spgs #2, CO. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 37° | 14° | 0.8" | 13.7" | 8 | 20° – 33° |
| February | 43° | 19° | 0.8" | 6.3" | 6 | 26° – 38° |
| March | 54° | 27° | 0.9" | 2.4" | 6 | 36° – 46° |
| April | 61° | 32° | 1.1" | 0.6" | 7 | 43° – 53° |
| May | 72° | 40° | 1.3" | 0.0" | 6 | 51° – 60° |
| June | 84° | 48° | 0.7" | 0.0" | 5 | 60° – 71° |
| July | 90° | 55° | 0.8" | 0.0" | 5 | 68° – 76° |
| August | 87° | 53° | 1.0" | 0.0" | 7 | 67° – 75° |
| September | 79° | 45° | 1.4" | 0.0" | 6 | 56° – 66° |
| October | 65° | 33° | 1.2" | 0.7" | 6 | 43° – 54° |
| November | 50° | 24° | 0.8" | 4.4" | 6 | 29° – 43° |
| December | 38° | 15° | 0.9" | 10.8" | 7 | 19° – 32° |
| Year | 63° | 34° | 11.8" | 38.9" | 75 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 29° to 43°. August is the most reliable, staying within 8°.
Where New Castle’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at New Castle’s center.
- Snow: Glenwood Spgs #2, CO.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Glenwood Spgs #2, CO, 12 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about New Castle’s climate
What is the weather like in New Castle?
A typical July afternoon reaches 90°, a January night drops to 14°, and about 39 inches of snow falls in a normal winter. Colder January nights than 87% of U.S. towns; hotter July afternoons than 78% of U.S. towns.
How cold does it get in New Castle in winter?
January nights average 14°. About 174 nights a year reach 32° or below and 6 reach 0° or below. In the coldest January of the last 30 years the month averaged 20°.
How much snow does New Castle get?
About 39 inches in a normal winter at Glenwood Spgs #2, CO, most of it in January.
How hot does it get in New Castle?
July, with a typical high of 90° and a low of 55°. About 39 days a year reach 90° (Glenwood Spgs #2, CO).
When is the first and last frost in New Castle?
In half of years the last spring frost (32°) comes by May 13 and the first fall frost by October 3, about 142 frost-free days, at Glenwood Spgs #2, CO.
What growing zone is New Castle in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −9°.
What is the best time of year to visit New Castle?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is New Castle getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 70% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in New Castle.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.